Mice transgenic for SV40 develop progressive glomerulosclerosis. We have postulated that the disease is due to an abnormal proliferative stimulus (T antigen) leading to mesangial proliferation. We are now investigating whether a stimulus known to induce renal hypertrophy results in an acceleration of the glomerular lesions. To that effect we have performed unilateral nephrectomies in SV40 6 weeks old mice and are examining the expression of T antigen and growth factors (IGF-I, TGF-B).